Model Scale and "Real" Flight of Generic UCAV and Advanced Combat Aircraft - An Industrial Perspective

Abstract

An industrial view on experimental and numerical investigations related to advanced combat aircraft needs is given. A critical comparison in between experimental and numerical results under wind tunnel conditions and real flight numerical simulations is presented. The Reynolds and Mach number influence on the aerodynamic behavior together with the development of the complex flowfields around generic UCAV configurations at transonic speed, medium and high angles of attack conditions is discussed. Static CFD results of forces and moments as well as the flow structure of the longitudinal and lateral flow conditions are compared to wind-tunnel measurements. Here combat aircraft and flying-wing type UCAV flow-phenomena of such as separation emerging at round and sharp leading edges into interacting vortex flows are shown. Also their possible development at transonic conditions causing interacting shock-systems are addressed. While wind-tunnel (low) Reynolds number, subsonic conditions are thought economic, they may be far off flight (high) Reynolds number and realistic subsonic and transonic Mach number speeds. Therefore also free-flight, full-scale conditions have been prepared to probe the possible differences with the experimental and numerical investigations of the design and early development process of future shapes. This will show the sensitivity and possible basic uncertainty of the stability & control investigations of modern combat aircraft due to insufficient full-scale, free-flight knowledge.